Method and devices for routing a message to a network server in a server pool

ABSTRACT

Method, devices and computer programs for routing a message to a first network server (MSC 1 ) in a server pool (CNSP) of a mobile communication system are disclosed. The mobile communication system comprises a controller (BSC 2 ) of an access network (AN) connectable to the first network server (MSC 1 ) and at least one further network server (MSC 2 ) in the server pool (CNSP), wherein service points are defined (S 100 ) and one or more of the service points are allocated (S 110 ) uniquely to each of the network servers (MSC 1 , MSC 2 ) in the server pool (CNSP). At least one of the network servers (MSC 1 , MSC 2 ) has allocated (S 110 ) at least two of the service points. A temporary identity is assigned (S 150 ) by the first network server (MSC 1 ) to a mobile device (MS). The temporary identity includes a selected service point which is selected (S 140 ) from the one or more service points allocated to the first network server (MSC 1 ). The temporary identity is transmitted (S 160 ) to the mobile device (MS) and a message (S 170 ) from the mobile device (MS) to the first network server (MSC 1 ) is routed (S 200 ) to the first network server (MSC 1 ) by extracting the selected service point from the temporary identity received by the mobile device (MS) and applying a routing algorithm to the selected service point. The routing algorithm reveals the first network server (MSC 1 ) from an analysis of the selected service point.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/469,360, filed May 7, 2004, which was the National Stage ofInternational Application No. PCT/EP02/02147, filed Feb. 28, 2002, thedisclosures of which are fully incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to the field of mobile communicationsystems, especially to a method for routing of a message to a networkserver in a server pool. Devices and computer programs embodying theinvention are also described.

BACKGROUND OF THE INVENTION

For identifying a subscriber in a mobile communication system like theGlobal System for Mobile Communication (GSM) or the Universal MobileTelecommunication System (UMTS), an International Mobile SubscriberIdentity (IMSI) is allocated uniquely and permanently to eachsubscriber. The IMSI is a number related to all network relatedsubscriber information and is stored in the Subscriber Identity Module(SIM) that is located in a mobile device like a mobile phone of thesubscriber. In addition, the IMSI is stored by a network server like theHome Location Register (HLR) and the serving Visitor Location Register(VLR). Unprotected transmission of the IMSI over the air interfacebetween the mobile device and the radio access network should be kept asseldom as possible to prevent misuse, e.g. to prevent an eavesdropperfrom accessing the IMSI for relating calls non-ambiguously to thesubscriber or to establish unauthorized roaming profiles of thesubscriber.

Protection is introduced into the mobile communication system usingtemporary identities whenever possible. These identities are aliases ofthe IMSI and are changed from time to time with typically localsignificance. Examples for such temporary identities are the TemporaryMobile Subscriber Identity (TMSI) used for circuit-switched (CS)connections and the Packet TMSI (P-TMSI) for packet switched (PS)connections.

A mobile device registered to the mobile communication system isassigned a temporary identity by a network server like a Mobile serviceSwitching Center (MSC) assigning the TMSI or a Serving General packetradio system Support Node (SGSN) assigning the P-TMSI. Depending on theconfiguration of the mobile communication system, an assignment of thetemporary identity can be triggered by the registration of the mobiledevice to the network server, by a call attempt, a service activation,or a location update, which is issued when the mobile device changes itslocation area (LA) for CS connections or routing area (RA) for PSconnections. The change of the LA or RA can be indicated to the networkserver by a change of a LA identity (LAI) or a RA identity (RAI)indicating the LA or RA, respectively. Other procedures triggering theassignment of a temporary identity are an expired or invalid temporaryidentity received by the network server.

The temporary identity as defined for GSM or UMTS is a number comprisingpredefined number blocks indicating a domain and a TMSI number. The sodefined temporary identity has a bit length of 32 bit and is sometimesalso named TMSI-Code (TIC). The number block representing the domainindicates whether the mobile device is registered in the CS or PSdomain. According to the present definition, the first two bits arereserved for the number block domain. The temporary identity issometimes used according to the TIC supplemented by a number blockreserved for the LAI or the RAI for TMSI or P-TMSI, respectively. Alsoother implementations of the temporary identities exist, e.g. in somesystems a TMSI generation may be included in the TIC for furtherassigning of already assigned TMSI numbers.

The 3GPP standard TS 29.002 v.4.2.1 (2000-12), chapter 8.1.4, for mobilecommunication systems allows to assign the temporary identity on a pernetwork server base, i.e. each assigned temporary identity has to beunique for each network server. 3GPP standard TS24.008 v4.1.1 (2001-01),chapter 4.3.1 and chapter 9.2.15, for mobile communications suggests toassign the temporary identity on a per LA/RA-base, wherein the networkserver assigning the temporary identity considers also locationinformation like the LAI or RAI and the temporary identity for a mobiledevice has to be unique within each LA or RA controlled by the networkserver, i.e. the same temporary identity that is assigned to a mobiledevice in a first LA of the network server can be assigned in a secondLA of the network server for a further mobile device at the same time.Referring to the availability of temporary identities, i.e. the maximumnumber of possible combinations of temporary identities that can beassigned, the assignment on a per LA/RA base is favorable. For anassignment on a per network server base, the availability is limited bythe number of combinations defined by the bit length of the TMSI number.Typically more than one LA or RA per network server exist and theavailability of temporary identities for an assignment on a per LA/RAbase is therefore much higher just because of the higher number ofLA/RAs per network server.

The introduction of a core network server pool, in the following namedserver pool, provides more flexibility to the mobile communicationsystem. In the server pool, many network servers are grouped such that amobile device can register to and can be controlled by any of thenetwork servers in the pool. The grouping can be achieved by connectinga controller of the access network with the network servers in theserver pool such that the controller is connected to each network serverin the server pool. Typically, there are many controllers in the accessnetwork that are connected to the network servers as described before.

The server pool is especially advantageous in situations wherein anetwork server in the server pool fails, is overloaded, or reveals otherdisturbances. For such situations, the mobile device can be registeredto and controlled by a further network server in the server pool thusimproving resilience of the mobile communication system with server poolcompared to the mobile communication system without server pool, i.e. amobile communication system wherein each controller is connected to onenetwork server only.

Owing to the fact that for a server pool one controller is connected tomultiple network servers, the routing of messages from a mobile deviceto the network server the mobile device is registered in becomes moredifficult. A server identifier is proposed to identify the networkserver in the server pool for routing a message from a mobile device.During registration of the mobile device to a first server of the serverpool, the first server sends its server identifier to the mobile device.Messages from the mobile device to the first network server can berouted to the first network server by analyzing the server identifier ina controller of an access network the mobile device is attached to.According to the document Introducing flexibility to the Iu interface,TSG-RAN Working Group Meeting #16, Windsor, UK, 16.-20. Oct. 2000,Agenda Item 12a), TSGR3#16(00)2586, the server identifier is proposed tobe a part of the TMSI, e.g. the server identifier is included into thetemporary identity. The server identifiers are allocated such that eachnetwork server has exactly one server identifier. A relation between theserver identifiers and the network servers in the server pool can beused to identify the network server from the server identifier comprisedin the messages from the mobile device for routing the messages to thenetwork server.

The introduction of the server identifier is essential for theimplementation of the server pool into the mobile communication system,because it provides a way to identify the network server for messagesfrom the mobile device to the network server where the mobile device isregistered. However, for the preferred implementation that the serveridentifier is included into the temporary identity, the availability oftemporary identities is reduced when the number of network servers inthe server pool is less than the number of server identifiers. Thenumber of server identifiers is given by the value according to the bitlength of the number block that is reserved within the temporaryidentity for including the server identifier. For example, a numberblock of 5 bit reserved for the server identifier relates to a maximumpossible number of 2⁵=32 network servers in the server pool. For thecase, that the network servers in the server pool do not equal themaximum possible number of network servers, i.e. when less than 32network servers are in the server pool, the fraction of the number ofserver identifiers exceeding the number of network servers in the serverpool remains unused. Following the present example, a server pool with 6network servers and 5 bit reserved for the server identifiers leads to asituation where 6 server identifiers are used for identifying uniquelythe network serves in the server pool whereas 24 server identifiers areleft unused. The same fraction of server identifiers that is left unuseddetermines the reduction of the availability of the temporary identitiesin the server pool. Following the present example, 6/32 of the temporaryidentities can be assigned and 24/32 are excluded from being assigned.Only for the special case that 32 network servers are in the serverpool, the maximum availability of temporary identities can be achieved.

In summary, the maximum availability can be only achieved when thenumber of network servers in the server pool equals the number of serveridentifiers defined by the bit length of the number block reserved forthe server identifier. However, this limitation is not acceptable for anoperator of a mobile communication system due to capacity and economicreasons.

U.S. Pat. No. 6,091,953 discloses a wireless communication system inwhich a signaling message from a mobile unit is routed by a messagerouter to a mobile switching center (MSC) serving the mobile unit in aserver pool. When a mobile unit attaches to the wireless communicationsystem, the message router assigns the mobile unit to one of the MSCs.The assigned MSC then assigns a temporary identity to the mobile unitthat identifies itself as the serving MSC. The temporary identityuniquely identifies the mobile unit. The mobile unit receives theassigned temporary identity from the serving MSC, stores the temporaryidentity and uses the temporary identity to identify itself in futuresignaling connections. The temporary identity is included in messagessent from the mobile unit to its serving MSC. The message router,reading the identity of the serving MSC from the temporary identityassigned to the mobile unit routes messages and traffic to the servingMSC. The message router can use a table mapping the MSC identifier to anetwork address for the routing. In order to embed the information aboutthe serving MSC in the temporary identity represented by a TMSI, all theavailable TMSI numbers in the network are portioned in n groups with nthe number of MSCs in the group and each MSC is assigned one of the ngroups. Furthermore, each four-byte TMSI is divided into two portions,wherein the first portion is used as the MSC identifier.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved method,devices and computer programs loadable into devices that provide anoptimized availability of temporary identities in a server pool of amobile communication system.

In the proposed method, a message is routed to a first network server ina server pool of a mobile communication system. The mobile communicationsystem comprises at least one controller of an access network. Thecontroller is connectable to the first network server and at least onefurther network server in the server pool. In the server pool, servicepoints are defined. The definition of the service points determines anumber of service points. Preferably, the number of services points isrelated to the number of network servers in the server pool and thenumber of service points exceeds the number of network servers operatingin the server pool. The definition of service points may be achieved bydetermining a number block reserved for the service points. The bitlength of the number block accordingly determines the number of servicepoints. The definition of the service points can comprise also thedetermination of the position of the number block reserved for theservice points in a temporary identity. The service points may bepreferably defined when the server pool is configured, e.g. by theoperator of the mobile communication system via Operation andMaintenance (O&M). The definition may vary from operator to operator ormay vary from server pool to server pool.

Furthermore, one or more of the service points that are defined for theserver pool are allocated uniquely to each of the network servers in theserver pool, i.e. each allocated service point is allocated in aone-to-one relation to one of the network servers. Preferably, allservice points that are defined are allocated to the network serversoperating in the server pool. Independent from the number of servicepoints and the number of network servers in the server pool, there is inany case at least one network server of the network servers in theserver pool that has allocated at least two of the service points. Asfor the definition of service points, the allocation of the servicepoints may also be achieved via O&M.

Definition and allocation of service points can be seen as steps for aconfiguration of the server pool and are prerequisites for the routingprocedure described in the following three paragraphs. The routingprocedure is typically carried out more often than the steps for theconfiguration.

A temporary identity is assigned by the first network server to a mobiledevice, e.g. when the mobile device is registered to the first networkserver or for a location update. The temporary identity includes aselected service point. The selected service point is selected from theone or more service points allocated to the first network server. Theone or more service points allocated to the first network server are asubset of the service points that are allocated to the network serversin the server pool. The selected service point is one service point ofthe subset and identifies uniquely the first network server.

The temporary identity that is assigned by the first network server istransmitted to the mobile device. The mobile device preferably storesthe received temporary identity.

A message from the mobile device to the first network server is routedto the first network server. The routing is achieved by first extractingthe selected service point from the temporary identity received by themobile device. Secondly, a routing algorithm is applied to the selectedservice point. The routing algorithm reveals the first network serverfrom an analysis of the selected service point, e.g. using the selectedservice point as input into the routing algorithm, the routing algorithmreveals as output an address of the first network server the selectedservice point is allocated to.

The proposed method for routing of messages to a network server in aserver pool optimizes the availability of temporary identities, becauseall of the service points that are defined by a number block in thetemporary identity can be allocated to the network servers in the serverpool. If all service points that are defined are allocated, no servicepoints are left unused, i.e. the number block reserved for the servicepoints is fully available for the assignment of temporary identities. Inthis case, the maximum availability of temporary identities is achievedand all temporary identities can be assigned. Also for the case, thatnot all service points that are defined are allocated, the proposedmethod ensures that the availability of temporary identities isoptimized. The reason is that the number of allocated service pointsexceeds the number of network servers operating in the server pool andthe number block reserved in the temporary identity for the servicepoints can be used more efficiently compared to prior art thus leavingless temporary identities unused. The number of excess service points,i.e. the difference between the number of the service points that aredefined and the number of network servers in the server pool, can beadjusted by the bit length of the number block reserved for the servicepoints. A slightly higher number of service points is easier to handleand to maintain while a significantly higher number provides moreflexibility such that particularities like different performances orcapacities of individual network servers in the server pool can beaddressed more adequately, e.g. the excess service points can beallocated in order to assign further temporary identities to networkservers that have more capacity to control mobile devices than othernetwork servers in the server pool. Furthermore, the proposed methodovercomes the limitation that the number of network servers directlydetermines the availability of temporary identities. Instead, any numberof network servers less than the number of service points can be chosenin the server pool while a maximum availability of temporary identitiescan be achieved.

According to a preferred embodiment, the routing algorithm is applied bythe controller of the access network. This implementation of the methodis advantageous compared to a possible alternative by applying therouting algorithm by the mobile device itself. This alternative may notbe preferred just because mobile devices that register to the serverpool have to be provided with the routing algorithm and may have to bemodified for executing the routing algorithm.

According to another preferred embodiment, the routing algorithmutilizes a table, which relates the allocated service points with thenetwork servers in the server pool. The routing algorithm can search thetable for an entry for the selected service point. The detected entryreveals the network server the selected service point is allocated to,i.e. the first network server according to the present notation. Fromthe knowledge of the first network server, the routing algorithm mayretrieve an address of the first network server from a separate columnof the table or a separate table correlating the network servers in theserver pool with the addresses of the network servers. Alternatively,the table utilized by the routing algorithm comprises the allocatedservice points uniquely related to the addresses of the network servers.For both alternatives, the routing algorithm outputs the address of thefirst network server from the selected service point. The message fromthe mobile device to the first network server can be subsequently routedto said address revealed from the routing algorithm.

According to another preferred embodiment, the temporary identity can beincluded in the message from the mobile device and the controller canextract the selected service point from the temporary identity. Thisprocedure is advantageous, because the mobile device does not have toprocess the temporary identity received from the first network server.When sending a message, the mobile device can retrieve the temporaryidentity from its storage and include the temporary identity into themessage. The controller receiving the temporary identity can extract theselected service point comprised in the received temporary identity forapplying the routing algorithm. The proposed procedure is fullycompliant with the processing of temporary identities by mobile devicesin present mobile communication systems such that mobile devices doesnot have to changed for implementing the proposed method.

According to another preferred embodiment, the mobile device can extractthe selected service point from the temporary identity and send theselected service point to the controller for applying the routingalgorithm. This procedure may require a modification of existing mobiledevices, but may be favorable in order to save processing effort at thecontroller for extracting the selected service point from the temporaryidentity. This embodiment may be especially helpful in situations whenmany messages from many mobile devices have to be routed by thecontroller at the same time.

According to another preferred embodiment, the number of service pointsis defined by selecting a bit length of a number block reserved for theservice points in the temporary identity. The number of service pointsmay have to be changed when the number of network servers approaches thenumber of service points or when more excess service points are neededto address more adequately inhomogeneities in the server pool. As anexample, if one of the network servers in the server pool is replaced bya new network server having significantly more capacity than the othernetwork servers in the server pool, the operator may change the bitlength of the number block reserved for the service points in order tocreate more excess service points. According to the present example, thenew network server may have allocated a significantly higher number ofservice points than the other network servers in the server pool. For achange of the number of service points, the operator may select a newbit length of the number block reserved for the service points in thetemporary identity. Especially the steps associated with the selectionof the selected service point, the assignment of the temporary identitywith included selected service point, the extraction of the selectedservice point, the routing algorithm, and optionally the tableutilizable by the routing algorithm may have to be modified to becapable to process a service point with changed bit length.

According to another preferred embodiment, the service points arere-allocatable to the network servers in the server pool. The number ofservice points allocated for each network server may be changedproviding more flexibility to the server pool, e.g. in order toaccommodate for particularities of the network servers in the serverpool or after a redefinition of the service points. After reallocationof one or more service points, the routing algorithm may have to beadapted for routing a message comprising one of the one or morereallocated service points.

According to another preferred embodiment, the service points can beallocated depending on a load of at least one of the network servers inthe server pool.

As an example, one or more service points that are defined but notalready allocated can be allocated depending on the load. Or alreadyallocated service points may be reallocated depending on the load. Orallocated service points may be removed from at least one of the networkservers depending on the load. The load of a network server can be autilization of a network server and may be supervised in an O&M centerof the network operator. As a measure for the load, the number oftemporary identities that are assigned by a network server to mobiledevices can be used. If the number of assigned temporary identitiescomes close to the availability of temporary identities of the networkserver, one or more further service points may be allocated via O&M tothe network server for increasing the availability of temporaryidentities of that network server. After the allocation, the networkserver can assign temporary identities including one of the one or morefurther service points. Consequently, the routing algorithm has to beupdated for routing messages comprising one of the one or more furtherservice points to the network server. The allocation depending on theload can be achieved statically or dynamically. An example for a staticallocation is to use predefined settings, e.g. according to expectedtraffic patterns for certain day times or weekly days like working daysand weekend in order to balance subscriber behavior and networkperformance. Dynamic allocation can be achieved by monitoring the loadof one or more network servers and adjusting the number of servicepoints accordingly.

According to another preferred embodiment, the service points can beallocated depending on a load of a link between the controller of theaccess network and one of the network servers in the server pool. Thisis especially advantageous if the number of mobile devices controllableby a particular network server is not limited by the capacity of theparticular network server itself but by the capacity of the link betweenthe particular network server and the controller. A congestion of thelink can be avoided by adapting the number of allocated service pointsto the capacity of the link. In addition, the link may carry alsofurther traffic. The number of server points allocated to the particularnetwork server may be adapted according to the load of the linkassociated with the number of mobile devices and the amount of thefurther traffic, i.e. more server points are allocated for lower furthertraffic and less are allocated for higher further traffic.

According to another preferred embodiment, the first network server canselect the selected service point from the one or more service pointsallocated to the first network server. The first network server mayselect the selected service point randomly or depending on theutilization of the one or more service points allocated to the firstnetwork server. Alternatively, the controller may select the selectedservice point introducing even more flexibility into the server pool.The drawback is that due to the much higher number of controllerscompared to network servers, the installation effort and maintenanceeffort is much higher.

According to another preferred embodiment, the temporary identity can beassigned based on location information of the mobile device. Thislocation information can be the LAI or RAI of the mobile device for PSand CS domain, respectively. The network server assigning the temporaryidentity can analyze the LAI or RAI and can select one of the one ormore service points that are allocated to the network server dependingon the result of the analysis.

According to another preferred embodiment, the service points are corenetwork server pool service points or location area service points. Corenetwork server pool service points are service points that are definedon a per network server base. A core network server pool service pointidentifies a service point within each server pool that can be used byany of the network servers of the server pool. The same network servercan make use of more than one core network server pool service point,but two different network servers cannot make use at the same time ofthe same core network server pool service point. Location area servicepoints are service points that are defined on a per LA/RA base. Alocation area service point identifies a service point within each LA/RAthat can be used by any of the network servers in the server pool. Thesame network server can make use of more than one location area servicepoint, but two different network servers cannot use the same locationarea service point. For indicating the LA or RA of the mobile device tothe network server, the LAI or RAI, respectively can be used. Temporaryidentities assigned on a per network server base are unique for eachnetwork server while temporary identities assigned on a per LA/RA baseare unique for each LA or RA.

According to another preferred embodiment, the network servers in theserver pool are mobile service switching centers (MSCs) or servinggeneral packet radio service support nodes (SGSNs).

According to another preferred embodiment, the temporary identity is atemporary mobile subscriber identity (TMSI) or a packet temporary mobilesubscriber identity (P-TMSI). Preferably, a number block reserved forthe service points is defined in the TMSI or P-TMSI while keeping thebit length of the TMSI or P-TMSI constant. Preferably, also the numberblock domain remains unchanged ensuring that at least mobile devices donot have to be modified with respect to the number block domain.

According to another preferred embodiment, the controller of the accessnetwork is a Base Station Controller (BSC) or a Radio Network Controller(RNC).

According to another preferred embodiment, the mobile communicationsystem is a global system for mobile communication (GSM) or a universalmobile telecommunication system (UMTS).

Correlatively, the present invention also concerns devices for executingthe proposed method. The devices can be adapted to all embodiments ofthe method as described above.

A network server exists in a server pool of a mobile communicationsystem. The network server is connectable to a controller of an accessnetwork and the network server has allocated at least two service pointsthat uniquely identify the network server in the server pool. Thenetwork server comprises a receiver, a transmitter, and a processingunit, wherein the receiver is adapted to receive a request for anassignment of a temporary identity for a mobile device. The request foran assignment of a temporary identity may origin from a location updateof the mobile device or a registration of the mobile device to thenetwork server. The processing unit is adapted to assign the temporaryidentity and to include one selected service point into the temporaryidentity. The selected service point is selected from the two or moreservice points allocated to the network server. The transmitter isadapted to send the assigned temporary identity to the mobile device.

A controller of an access network exists in a mobile communicationsystem. The controller is connectable to a first network server and atleast one further network server in a server pool. The controllercomprises a receiver, a transmitter, and a processing unit, wherein thereceiver is adapted to receive a message from a mobile device to thefirst network server. The message comprises a selected service point,which is uniquely allocated to the first network server. The processingunit is adapted to apply a routing algorithm to the selected servicepoint. The routing algorithm reveals the first network server from ananalysis of the selected service point by utilizing a table. The tablecomprises service points allocated uniquely to the network servers inthe server pool. In the table, at least one of the network servers hasallocated at least two service points and one of the service points inthe table is the selected service point identifying the first networkserver. The transmitter is adapted to send the message to the firstnetwork server.

The present invention also concerns computer programs, each of thecomputer programs being loadable into a processing unit of acorresponding device. The computer programs comprise portions ofsoftware codes in order to implement the method as described above whenoperated by the corresponding device. The computer programs can bestored on computer readable media. A computer-readable medium can be apermanent or rewritable memory within a device or located externally.The computer programs can be also transferred to the devices for examplevia a cable or a wireless link as a sequence of signals.

A computer program is loadable into a processing unit of a networkserver in a server pool of a mobile communication system. The networkserver is connectable to a controller of an access network. The networkserver has allocated at least two service points that uniquely identifythe network server in the server pool. The computer program comprisescode adapted to process a request for an assignment of a temporaryidentity for a mobile device, to assign the temporary identity and toinclude one selected service point into the temporary identity. Theselected service point is selected from the two or more service pointsallocated to the network server. The computer program further comprisescode to initiate a transmission of the assigned temporary identity tothe mobile device.

A computer program is loadable into a processing unit of a controller ofan access network of a mobile communication system. The controller isconnectable to a first network server and at least one further networkserver in a server pool. The computer program comprises code adapted toapply a routing algorithm to a selected service point included in amessage from a mobile device to the first network server. The selectedservice point is uniquely allocated to the first network server and therouting algorithm reveals the first network server from an analysis ofthe selected service point by utilizing a table comprising servicepoints allocated uniquely to the network servers in the server pool. Inthe table, at least one of the network servers has allocated at leasttwo service points and one of the service points in the table is theselected service point identifying the first network server. Thecomputer program comprises code adapted to initiate a sending of themessage to the first network server.

In the following, detailed embodiments of the present invention shall bedescribed in order to give the skilled person a full and completeunderstanding. However, these embodiments are illustrative and notintended to be limiting, as the scope of the invention is defined onlyby the appended claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 a shows a flow-chart diagram of a first embodiment of theproposed method;

FIG. 1 b shows processes and messages by devices adapted to perform thefirst embodiment of the proposed method;

FIG. 2 a shows a structure of a temporary identity according to priorart;

FIG. 2 b shows a structure of a temporary identity with number block forserver identifiers for use in a server pool according to prior art;

FIG. 2 c shows a structure of a temporary identity with number block forservice points for use in a server pool according to the presentinvention;

FIG. 3 a shows a table for illustrating the availability of temporaryidentities in a server pool according to prior art wherein the temporaryidentities are assigned on a per network server base;

FIG. 3 b shows a table for illustrating the availability of temporaryidentities in a server pool according to the present invention whereinthe temporary identities are assigned on a per network server base;

FIG. 4 a shows a table for illustrating the availability of temporaryidentities in a server pool according to prior art wherein the temporaryidentities are assigned on a per LA/RA base;

FIG. 4 b shows a table for illustrating the availability of temporaryidentities in a server pool according to the present invention whereinthe temporary identities are assigned on a per LA/RA base;

FIG. 5 shows a flow of tables indicating an allocation of service pointsto network servers in the server pool for different states of the serverpool;

FIG. 6 shows a first example for a mobile communication systemcomprising network servers of a server pool, controllers of an accessnetwork, a mobile device, and connections for exchanging messagesbetween the individual devices;

FIG. 7 a shows a second example of a mobile communication system adaptedto assign temporary identities on a per network server base according tothe present invention;

FIG. 7 b shows a third example of a mobile communication system adaptedto assign temporary identities on a per LA/RA base according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 a shows a flow chart diagram of a first embodiment of theproposed method and FIG. 1 b shows an example of messages and processesexecuted by devices for carrying out the proposed method according tothe flow-chart diagram in FIG. 1 a. Depending on the implementation orcase, it may be advantageous to integrate additional processes ormessages like a confirmation of a process or message before the nextprocess or message, respectively, is executed in order to ensure thatthe previous process or message, respectively, has been carried outcorrectly or just to acknowledge the correct transmission of a message.

The proposed method starts with a configuration of the server pool CNSPwherein service points are defined S100 and allocated S110. According tothe present example, the server pool CNSP comprises a first networkserver MSC1 and a further network server MSC2. Both network serversMSC1;MSC2 in this example are of the same type with the type beingeither MSC or SGSN. First of all, the service points in the server poolCNSP are defined S100: A number of service points may be defined by anumber block reserved for the service points in a temporary identity.Also, the position of the number block within the temporary identity canbe defined. The service points are preferably defined S100 by theoperator of the mobile communication system who may consider the actualor future number of network servers in the pool for the definition ofthe number of service points. A requirement of the proposed method isthat the service points are defined S100 such that the number of servicepoints exceeds the number of network servers MSC1; MSC2 operating in theserver pool CNSP. In addition, the operator may also take into accountthe actual or future capacity or utilization of each of the networkservers MSC1; MSC2. Based on these considerations, the service pointscan be defined S100 such that the number of service points exceeds thenumber of network servers MSC1; MSC2 slightly or significantly, e.g. inorder to achieve an easier processing or more flexible allocation of theservice points in the following processes, respectively. Alternatively,the number block in the temporary identity may be standardized such thatthe total bit length and the position is fixed. In this case, theservice points cannot be defined S100 by the operator.

The service points that are defined S100 can be allocated S110 to thenetwork servers MSC1; MSC2 in the server pool CNSP. Preferably, allservice points that are defined S100 are allocated S110 to achieve themaximum availability of temporary identities. However, the server poolCNSP may also be configured such that not all defined S100 servicepoints are allocated S110 for the expense of a reduced availability ofthe temporary identities. Not allocated service points may be allocatedS110 in a situation when a device like a network server or link failsand a spare device has to be activated for replacing or bypassing thefailed device. The allocation of not allocated service points to thespare device may be executed faster or easier than reallocating servicepoints that are allocated S110 to further network servers to the sparenetwork server. In any case, at least one of the network servers hasallocated at least two service points. Depending on the number of excessservice points, many service points may be allocated to many networkservers. As an example, a server pool having 3 network servers has 64service points according to a number block reserved for the serverpoints with a bit length of 6. A possible distribution of the 64 servicepoints to the three network servers may be 15 service points allocatedto the first network server, 15 service points allocated for the secondnetwork server and 34 service points for the third network server. Ingeneral, the service points can be allocated S110 homogeneously ornon-homogeneously, statically or dynamically to the network serversMSC1; MSC2 in the server pool CNSP. However, maximum flexibility andperformance is achieved for a dynamic allocation taking into accountindividual performances and loads of network servers MSC1; MSC2 andlinks of the server pool CNSP. When the service points are allocatedS110, a selection function may be provided to the network servers MSC1;MSC2. The selection function can be used by the individual networkserver to select a service point from the service points that areallocated S110 to the individual network server. The selection functionmay consider supplementary information like the number of alreadyassigned temporary identities for each service point that is allocatedS110 to the network server. The selection function may be updated viaO&M by the network operator after a reallocation and may be transmittedto the network servers MSC1; MSC2 in the server pool CNSP. In addition,a routing algorithm is provided to the controllers like BSCs or RNCs ofthe access network AN. When applied S190 to one of the allocated servicepoints, the routing algorithm outputs the network server said servicepoint is allocated S110 uniquely to. Preferably, the routing algorithmutilizes a table that reveals the relation between the service pointsthat are allocated S110 and the network servers MSC1; MSC2 in the serverpool CNSP, e.g. by correlating the allocated service points with theaddresses of the network servers MSC1; MSC2 in the server pool CNSP.After a reallocation of service points, the table is preferably updatedaccordingly.

A mobile device MS that registers S120 to the mobile communicationsystem within the coverage of the access network AN of the server poolCNSP, attaches first to a controller BSC2 of the access network AN. Thecontroller BSC2 can be a BSC or RNC for a GSM or UMTS system,respectively, and may execute a selection S130 of one of the networkservers MSC1; MSC2 in the server pool CNSP. The controller BSC2 may usea list that comprises the network servers MSC1; MSC2 in the server poolCNSP. For the selection S130 of one of the network servers MSC1; MSC2,the controller BSC2 may take into account location information of themobile device MS, of the controller BSC2 or of one or more of thenetwork servers MSC1; MSC2 or may consider capacity or utilizationinformation, e.g. indicating the capacity or load of a link or at leastone of the network servers MSC1; MSC2. According to FIG. 1, thecontroller BSC2 executes the selection S130 of the first network serverMSC1. The selection S130 may include a transmission of a message S135 tothe selected network server informing the first network server MSC1about the selection S130. The step where the mobile device MS registersS120 may be replaced by a message that indicates a change of thelocation area of the mobile device MS to the first network server MSC1(location update not shown in FIG. 1). The selection S130 of one of thenetwork servers MSC1; MSC2 in the server pool CNSP can be skipped in thecase of a location update. All following messages and processes for alocation update can be processed accordingly to the followingdescription of FIG. 1.

One of the one or more service points allocated to the first networkserver MSC1 is selected S140, e.g. by the first network server MSC1. Theselected service point may be selected S140 based on the availability oftemporary identities. A temporary identity for the mobile device isassigned S150 by the first network server MSC1 and the selected servicepoint is included into the temporary identity. The temporary identity istransmitted S160 from the first network server MSC1 to the mobile deviceMS, where the received temporary identity can be stored.

The temporary identity can be used for routing a message S170 from themobile device MS to the first network server MSC1. The mobile device MScan retrieve the stored temporary identity and include the temporaryidentity into a message S170 to be sent first to the controller BSC2where the mobile device MS is attached to. The temporary identity may bedetected by the controller BSC2 and the selected service point can beextracted S180 by the controller BSC2 from the temporary identity.Alternatively, the mobile device MS may extract the selected servicepoint from the temporary identity and send the selected service point tothe controller BSC2 for further routing of the message S170. In thealternative case, the controller does not have to extract the selectedservice point from the temporary identity (alternative case not shown inFIG. 1). For identifying the first network server MSC1 associated withthe selected service point, the routing algorithm can be applied S190 bythe controller BSC2 to the selected service point, e.g. it can besearched in a table revealing the correlation of the service pointsallocated to the network servers in the server pool for an entry for theselected service point. The entry can reveal an address of the firstnetwork server MSC1. From the knowledge of the address of the firstnetwork server MSC1, the message S170 or one or more further messagescan be routed S200 to the first network server MSC1.

For one or more further messages from the mobile device MS to the firstnetwork server MSC1, the mobile device MS may include the temporaryidentity or the selected service point into all of the further messages.The one or more further messages can hence be routed S200 to the firstnetwork server MSC1 according to the proposed method as describedbefore. Alternatively, the first network server MSC1 or the controllerBSC2 may assign a temporary identifier that may be used for routing thefurther messages from the mobile device MS within the duration of aconnection, e.g. for a voice call or data session. By assigning atemporary identifier, a logical channel can be opened that concatenatesfollowing messages as it is commonly applied for example in a dialog.Typically a temporary identifier is a number block of less digits thanthe temporary identity thus saving transmission cost and processingeffort. When the connection is released, the temporary identifier isinvalidated and the mobile device MS can use the temporary identity forsubsequent messages to the first network server MSC1.

FIG. 2 a shows the structure of the temporary identity when the serverpool CNSP is not supported. The temporary identity is a number block ofa certain bit length BL. Currently, the TMSI and P-TMSI are specified tohave a bit length BL of 32 bit. The structure contains the number blockD having a bit length d of 2 bit reserved for the domain and the numberblock TN for the TMSI number having a bit length tn of 30 bit.

FIG. 2 b shows a structure of the temporary identity for use in a serverpool CNSP according to prior art. This temporary identity can becomposed of a number block D reserved for the domain, a number block SIDreserved for the server identifier, and a number block TN reserved forthe TMSI number.

FIG. 2 c shows a preferred structure of the temporary identity for usein a server pool CNSP according to the present invention. The temporaryidentity can be composed of a number block D reserved for the domain, anumber block SP reserved for the service point, and a number block TNreserved for the TMSI number. The bit length n of the number block SPreserved for service points or the bit length x of the number block TNreserved for TMSI numbers may be standardized or may be set by theoperator of the respective server tool. The corresponding applies forthe relative position of the number blocks D; SP; TN within thetemporary identity. For compatibility reasons, the bit length BL of thetemporary identity for the server pool CNSP according to the presentinvention preferably equals the bit length BL of the temporary identityas shown in FIG. 2 a. The corresponding applies for the bit length d andposition of the number block D for the domain. Note that only for thefollowing comparisons on the availability of temporary identities forthe server pool CNSP according to prior art and for the presentinvention, the bit length n of the number block SID reserved for theserver identifier and the bit length n of the number block SP reservedfor the service point have been chosen identically. The correspondingapplies to the bit length x for the number block TN reserved for theTMSI number in FIG. 2 b and FIG. 2 c. Furthermore, the proposed methodcan be applied to temporary identities comprising a number block forTMSI generation. However, a number block for TMSI generation is notconsidered in the following descriptions.

In FIGS. 3 a and 3 b, the availabilities of temporary identities for aserver pool CNSP according to prior art and according to the presentinvention, respectively, are evaluated for an assignment on a pernetwork server base. For comparison, the temporary identities arestructured according to FIGS. 2 b and 2 c, respectively, as explainedabove. Only the number block SID, the number block SP, and the numberblock TN have been considered in the following evaluation. The numberblock D has been not considered as this block is reserved for theindication of the domain.

The table in FIG. 3 a shows in its first column the server identifiers(SID) which are available for a number block SID of a bit length n of nbits. The number of service points which can be defined S100 by such anumber block SID reserved for server identifiers according to FIG. 2 bis 2^(n). In the present example, the server pool CNSP has three networkservers, which are denoted by MSC1, MSC2, and MSC3 in the second columnof the table. Only three of the server identifiers can be allocated tothe network servers in the server pool CNSP. The number of not allocatedserver identifiers amounts to the difference between the number ofserver identifiers (2^(n)) according to the bit length n of the numberblock SID reserved for server identifiers and the number of networkservers (N_(NS)) in the server pool, i.e. 2^(n)−N_(NS) for the number ofnot allocated server identifiers. In the third column, the maximumnumber of TMSI numbers (C_(SID)) that can be assigned for each serveridentifier that is allocated in the server pool CNSP is shown. Accordingto the bit length x of x=BL−n−d bit, the maximum number of TMSI numbersamounts to 2^(x) for each allocated server identifier. Due to the fact,that 2^(n)−N_(NS) service identifiers are not allocated, thecorresponding TMSI numbers are excluded from being used for theassignment of temporary identities. These excluded TMSI numbers areindicated by “--” in the table. The following formula (1a-b) calculatesthe availability (N_(A)) of temporary identities of a server pool CNSPaccording to prior art for an assignment on a per network server basewithout considering the number block D. $\begin{matrix}{N_{A} = {\sum\limits_{{SID} = 0}^{{SID} = {N_{NS} - 1}}C_{SID}}} & \left( {1\quad a} \right) \\{{= {N_{NS}*2^{x}}}\quad} & \left( {1\quad b} \right)\end{matrix}$

Basically, the formula (1a) calculates the sum over the maximum numberof TMSI numbers (C_(SP)) for server identifiers allocated to networkservers in the server pool CNSP. For the present example of threenetwork servers, the result of 1b) is 3*2^(x). Obviously, the2^(n)−N_(NS) server identifiers, which are not allocated, do notcontribute to the sum. Only for the case that the number of networkservers equals the number of allocated server identifier, the maximumavailability of temporary identities in a server pool CNSP can beachieved, i.e. for N_(NS)=2^(n). However, the number of network serversin a server pool CNSP is preferably chosen according to the number ofsubscribers expected to be covered by the server pool CNSP. In mostcases, the number of network servers is less than 2^(n) at the expenseof a reduction of the availability of temporary identities.Alternatively, matching the number of network servers with the number ofservice points for achieving a maximum availability of temporaryidentities is often not recommended due to economic reasons. In summary,the determination of the availability of temporary identities by thenumber of network servers is not acceptable in many situations.

FIG. 3 b shows a table for a corresponding situation as in FIG. 3 amodified for a server pool CNSP according to the present invention.Obviously, the server identifiers (SID) are replaced by the servicepoints (SP) in FIG. 3 b. In the first column, the 2^(n) service pointsthat are defined S100 by the number block SP of bit length n are shown.All 2^(n) service points are allocated S110 to the three network serversMSC1, MSC2, and MSC3 in the server pool CNSP. The network servers canhave allocated multiple service points such that no service point isleft unused as shown in column two. The third column shows the maximumnumber of TMSI numbers that can be assigned for each allocated servicepoint (C_(SP)). According to the present example of a bit length x ofthe number block reserved for the TMSI number, the available TMSInumbers per service point (C_(SP)) amounts to be 2^(x) for each servicepoint as in the previous example in FIG. 3 a. In contrast to the tablein FIG. 3 a, the third column is completed in FIG. 3 b, because allservice points are allocated S110. The following formula (2a-b) givesthe availability (N_(A)) of temporary identities that can be assignedfor a server pool CNSP on a per network server base according to thepresent invention without considering the number block D.$\begin{matrix}{N_{A} = {\sum\limits_{{SP} = 0}^{{SP} = {2^{n} - 1}}C_{SP}}} & \left( {2\quad a} \right) \\{{= {2^{n}*2^{x}}}\quad} & \left( {2\quad b} \right)\end{matrix}$

For a temporary identity as defined in FIG. 2 c, the formula calculatesessentially the sum over all TMSI numbers per service point (C_(SP)) incolumn three for all service points given in column one. Due to the factthat all service points are allocatable to any number of network serversin the server pool CNSP, the maximum availability of temporaryidentities is achievable independent from the number of network serversin the server pool CNSP. In contrast to prior art, the number of networkservers in the server pool CNSP can be freely chosen, e.g. the number ofnetwork servers can be matched to the number of subscribers expected forthe server pool CNSP. In addition, the maximum availability of temporaryidentities can always be achieved if all service points that are definedS100 by a number block in the temporary identity are allocated S110 tothe network servers in the server pool CNSP. According to the presentinvention, the number of network servers does not limit the availabilityof the temporary identities.

The table in FIG. 4 a reflects a corresponding situation as the tablegiven in FIG. 3 a with the difference that temporary identities are nowassigned on a per LA/RA base instead of a per network server base. Inthe present example there are three network servers MSC1, MSC2, and MSC3and two location areas per network server, i.e. LA1 and LA2. Thelocation areas are indicated by LA_(ij) with i=1, 2, 3 being the numberfor the network server and j=1, 2 being the number for the LA (differentindexing can mean the same location area). The number of LAs and theLA_(ij) given for each of the server identifiers that are allocated tothe network servers are given in column four of the table. Theavailability (N_(A)) of temporary identities for a server pool CNSPaccording to prior art for an assignment on a per LA/RA base can becalculated according to following formula (3a-b) without considering thenumber block D. $\begin{matrix}{N_{A} = {\sum\limits_{{SID} = 0}^{{SID} = {N_{NS} - 1}}{C_{SID}*L_{SID}}}} & \left( {3\quad a} \right) \\{N_{A^{\prime}} = {N_{NS}*2^{x}*2}} & \left( {3\quad b} \right)\end{matrix}$

(3a) calculates the availability (N_(A)) for an arbitrary number ofnetwork servers and an arbitrary number of location areas per allocatedserver identifier, (3b) calculates the availability (N_(A′)) for 2location areas per allocated server identifier. For the present exampleof three network servers and two location areas, the availabilityamounts to 3*2^(x)*2. The availability of temporary identities isincreased for an assignment on a per LA/RA base compared to theassignment on a per network server base just because of the typicallyhigher number of location areas. This can be easily seen from comparingFIG. 4 a with FIG. 3 a and formula (3a-b) with (1a-b). However, also forthe assignment on a per LA/RA base temporary identities are left unusedin the case that the number of network servers (N_(NS)) does not equalthe number of server identifiers of 2^(n).

FIG. 4 b shows a table for a corresponding situation as in FIG. 4 amodified for a server pool CNSP according to the present invention.Obviously, the server identifiers (SID) are replaced by the servicepoints (SP) in FIG. 3 b. All 2^(n) defined service points of column oneare allocated S110 to the three network servers MSC1, MSC2, and MSC3 incolumn two. In column three and four the number of TMSI numbers that canbe assigned for each allocated service point and the correspondingnumber of LAs with the LA_(ij), respectively, are given according to thepresent example. The following formula (4a-b) can be used to calculatethe availability of temporary identities accordingly without consideringthe number block D. $\begin{matrix}{N_{A} = {\sum\limits_{{SP} = 0}^{{SP} = {2^{n} - 1}}{C_{SP}*L_{SP}}}} & \left( {4\quad a} \right) \\{N_{A^{\prime}} = {2^{n}*2^{x}*2}} & \left( {4\quad b} \right)\end{matrix}$

Again, the availability of temporary identities is not limited by thenumber of network servers in the server pool CNSP and the maximumavailability is achieved when all service points are allocated S110. Asit can be easily seen from a comparison of formula (4a-b) with formula(2a-b), the assignment on a per LA/RA base increases the availabilitycompared to the assignment on a per network server base due to thetypically higher number of LA/RAs.

FIG. 5 shows a flow of tables for illustrating modifications in a serverpool CNSP that can be executed according to the present invention. Inthe first column, the service points according to a number block of 3bit are given translating into a total number of 2³=8 service points.The first table represents a first state T1 of the server pool CNSPcomprising two network servers MSC1 and MSC2. All 8 service points areallocated S110 to the two network servers MSC1 and MSC2 giving a maximumavailability of temporary identities as also indicated by the number ofTMSI numbers in completed column three. The second table reflects asecond state T2 different from the first state T1. A new network serverMSC3 is introduced into the server pool CNSP by removing the servicepoint 7 from MSC2 and allocating the removed service point 7 to MSC3.The third table reflects a third state T3 of the server pool CNSPdifferent from the first and second states T1; T2. Service points 5 and6 are removed from MSC2 and MSC1, respectively, and are allocated S110to MSC3. In all depicted states T1; T2; T3, the maximum availability oftemporary identities is achieved independent from the number of networkservers in the server pool CNSP. Depending on the implementation orcase, the allocation of the service points may be preferably executedservice point by service point in order to avoid congestion of links inthe core network as explained in detail later on.

It is also possible to decrease the number of service points allocatedS110 to a network server, e.g. in order to reduce its load. In the thirdstate T3, MSC3 has allocated S110 the service points 5, 6, and 7. In asituation, when MSC3 reveals errors or needs to be upgraded, the load ofMSC3 can be reduced by reducing the availability of temporary identitiesfor MSC3. The reduction of the availability can be achieved by areduction of the service points allocated to MSC3. When changing fromstate T3 to state T2 according to the present example, service points 5and 6 are removed from MSC3 thus reducing the load of MSC3 by 67%. Themaximum availability of temporary identities is maintained in the serverpool CNSP, when the removed service points 5 and 6 are allocated S110 tothe further network servers in the server pool, i.e. to MSC2 and MSC1according to the present example. Disconnecting a network server fromthe server pool CNSP can be achieved by removing all service points froma network server, e.g. for disconnecting MSC3 this may be achieved bystarting from the third state T3 to the first state T1 or from thesecond state T2 to the first state T1.

FIG. 5 reveals modifications of a server pool CNSP for an assignment oftemporary identities on a per network server base. However, it isobvious from the previous explanations given especially with respect toFIGS. 3 and 4 to expand the tables and the corresponding explanations ofFIG. 5 for an assignment on a per LA/RA base.

Preferably, service points are gradually allocated S110 to a networkserver, e.g. service point by service point in order to avoid peaks inthe signalling load within the core network. For example if a newnetwork server is added to a server pool CNSP and one or more servicepoints are allocated, the new network server lacks of subscriber data.When mobile devices register to the newly introduced network server, thenetwork server requests subscriber data related to the mobile device MSfrom the HLR. By allocating only one or a few service points when addingthe network server to the server pool CNSP, the fraction of mobiledevices within the server pool CNSP that are served by the newlyintroduced network server increases slowly thus avoiding congestion ofthe core network signalling between the newly introduced network serverand the HLR. Generally, such congestion can be avoided by allocating alimited number of service points per time period.

FIG. 6 shows an example for a communication system according to thepresent invention. A server pool CNSP comprising two network serversMSC1; MSC2, an access network AN comprising three controllers BSC1;BSC2; BSC3 and a mobile device MS are depicted. A characteristic featureof the server pool CNSP are the links C11; C12; C13; C21; C22; C23between the network servers MSC1; MSC2 and the controllers BSC1; BSC2;BSC3. Per definition of the server pool CNSP, each of the controllersBSC1, BSC2, BSC3 is connectable to each of the network servers MSC1;MSC2 in the server pool CNSP thus enabling each mobile device to beserved by any of the network servers MSC1; MSC2 in the server pool CNSP.According to FIG. 6, the mobile device MS is attached via the wirelesslink Cmobile to the controller BSC2 of the access network AN. When themobile device MS registers S120 to the server pool CNSP, the controllerBSC2 performs a selection S130 of one of the network servers MSC1; MSC2in the server pool CNSP to control the mobile device MS. The selectednetwork server, i.e. for example the first network server MSC1, proceedssuch that one service point from the one or more service pointsallocated S110 to the first network server MSC1 is selected S140, atemporary identity for the mobile device MS is assigned S150, and theselected service point is included into the assigned temporary identitywhich is subsequently transmitted S160 via link C12 and link Cmobile tothe mobile device MS. For example during a call setup the mobile deviceMS sends a message S170 for the first network server MSC1 to thecontroller BSC2 via link Cmobile. The message S170 comprises thetemporary identity assigned to the mobile device MS by the first networkserver MSC1. The controller BSC2 detects the temporary identity and theselected service point comprised in the temporary identity is extractedS180 by the controller BSC2. Alternatively, the mobile device canextract the selected service point from the temporary identity and cansend selected service point to the controller BSC2 via link Cmobile. Foridentifying the first network server MSC1 associated with the selectedservice point, a routing algorithm is applied S190 by the controllerBSC2 to the selected service point. The selected service point isanalyzed, e.g. it is searched in a table accessible by the controllerBSC2 for an entry for the selected service point. The detected entryreveals an address of the first network server MSC1. From the knowledgeof the address of the first network server MSC1, the message S170 andoptionally one or more further messages can be routed S200 by thecontroller BSC2 to the first network server MSC1 via link C12. If thefirst network server MSC1 is not accessible e.g. due to a disturbance ofthe first network server MSC1 or of the link C12 between the controllerBSC2 and the first network server MSC1, the controller BSC2 may selectone further network server MSC2 in the server pool CNSP for controllingthe mobile device MS, e.g. via link Cmobile and link C22.

FIGS. 7 a and 7 b show two further examples for a mobile communicationsystem adapted to execute the method according to the present inventionon a per network server base and a per LA/RA base, respectively. Themobile communication system comprises a core network CN comprising afirst server pool CNSP and a second server pool CNSP2. The first serverpool CNSP comprises two network servers MSC1; MSC2, e.g. MSCs, and thesecond server pool CNSP2 comprises two network servers MSC3; MSC4, e.g.SGSNs. In addition, FIG. 7 b depicts also a first location/routing areaLARA1 of the first server pool CNSP and a second location/routing areaLARA2 of the second server pool CNSP2. Core network server pool servicepoints for an assignment of temporary identities on a per network serverbase and location area service points for an assignment of temporaryidentities on a per LA/RA base are depicted in FIG. 7 a and 7 b,respectively. Two mobile devices MS; MS2 controlled by the first networkserver MSC1 in the first server pool CNSP are shown in both figures.

In FIG. 7 a, both mobile devices MS; MS2 are controlled by the samenetwork server MSC1, but the mobile devices MS; MS2 are assigned todifferent core network server pool service points. This means that bothmobile devices MS; MS2 can have the same domain and the same TMSI numbervalues in the temporary identity, even though the temporary identity TIaof the first mobile device MS is different from the temporary identityTI2 a of the second mobile device MS2 due to the different core networkserver pool service points.

In FIG. 7 b, both mobile devices MS; MS2 are controlled by the samenetwork server MSC1, but the mobile devices MS; MS2 are assigned todifferent location area service points. This means that both mobiledevices MS; MS2 can have the same domain and the same TMSI number valuesin the temporary identity, even though the temporary identity TIb of thefirst mobile device MS is different from the temporary identity TIb ofthe second mobile device MS2 due to the different location area servicepoints.

The above embodiments admirably achieve the objects of the invention.However, it will be appreciated that departures can be made by thoseskilled in the art without departing from the scope of the inventionwhich is limited only by the claims.

1. Method for operating a network server (MSC1) in a server pool (CNSP)of a mobile communication system, the server pool having at least onefurther network server (MSC2), the network server (MSC1) beingconnectable to a controller (BSC2) of an access network (AN), thenetwork server (MSC1) having allocated at least two service points thatuniquely identify the network server (MSC1) in the server pool (CNSP),the method comprising the steps of: receiving a request for anassignment of a temporary identity for a mobile device (MS); assigningthe temporary identity and including one selected service point beingselected from the two or more service points allocated to the networkserver (MSC1) into the temporary identity; and sending the assignedtemporary identity to the mobile device (MS).
 2. The method according toclaim 1, further comprising the step of re-allocating the service pointsto the network servers (MSC1, MSC2) in the server pool (CNSP).
 3. Themethod according to claim 2, wherein the service points are allocateddepending on a load of at least one of the network servers (MSC1 MSC2)in the server pool (CNSP).
 4. The method according to claim 2, whereinthe service points are allocated depending on a load of a link betweenthe controller (BSC2) of the access network (AN) and one of the networkservers (MSC1, MSC2) in the server pool (CNSP).
 5. The method accordingto claim 1, wherein the network server (MSC1) selects the selectedservice point.
 6. The method according to claim 1, wherein the temporaryidentity is assigned based on location information of the mobile device(MS).
 7. The method according to claim 1, wherein the controller (BSC2)of the access network (AN) is a base station controller or a radionetwork controller.
 8. The method according to claim 1, wherein themobile communication system is a global system for mobile communicationor a universal mobile telecommunication system.
 9. A method foroperating a controller (BSC2) of an access network (AN) of a mobilecommunication system, the controller (BSC2) being connectable to a firstnetwork server (MSC1) and at least one further network server (MSC2) ina server pool (CNSP), the method comprising the steps of: receiving amessage from a mobile device (MS) to the first network server (MSC1),the message comprising a selected service point which is uniquelyallocated to the first network server (MSC1); applying a routingalgorithm to the selected service point, the routing algorithm revealingthe first network server (MSC1) from an analysis of the selected servicepoint by utilizing a table comprising service points allocated uniquelyto the network servers (MSC1, MSC2) in the server pool (CNSP), in thetable at least one of the network servers (MSC1, MSC2) having allocatedat least two service points and one of the service points in the tablebeing the selected service point identifying the first network server(MSC1); and sending the message to the first network server (MSC1). 10.The method according to claim 9, wherein the temporary identity isincluded in the message from the mobile device (MS), further comprisingthe step of extracting the selected service point from the temporaryidentity.
 11. The method according to claim 9, further comprising thestep of receiving the selected service point from the mobile device(MS), the selected service point being extracted from the temporaryidentity by the mobile device (MS).
 12. The method according to claim 9,wherein the controller (BSC2) of the access network (AN) is a basestation controller or a radio network controller.
 13. The methodaccording to claim 9, wherein the mobile communication system is aglobal system for mobile communication or a universal mobiletelecommunication system.
 14. A method for sending a message from amobile device (MS) to a first network server (MSC1) in a server pool(CNSP) of a mobile communication system, the mobile communication systemhaving a controller (BSC2) of an access network (AN) connectable to thefirst network server (MSC1) and at least one further network server(MSC2) in the server pool (CNSP), wherein service points are defined andone or more of the service points are allocated uniquely to each of thenetwork servers (MSCI, MSC2) in the server pool (CNSP), at least one ofthe network servers (MSC1, MSC2) having allocated at least two of theservice points, the method comprising the steps of: receiving atemporary identity including a selected service point being selectedfrom the one or more service points allocated to the first networkserver (MSC1); extracting the selected service point from the temporaryidentity; and sending the selected service point to the controller(BSC2) for applying a routing algorithm for routing the message to thefirst network server (MSC1).
 15. The method according to claim 14,wherein a number of service points in the server pool is defined byselecting a bit length (n) of a number block (SP) reserved for theservice points in the temporary identity.
 16. The method according toclaim 14, wherein the service points are core network server poolservice points or location area service points.
 17. The method accordingto claim 14, wherein the network servers (MSC1, MSC2) in the server pool(CNSP) are mobile service switching centers or serving general packetradio service support nodes.
 18. The method according to claim 14,wherein the temporary identity is a temporary mobile subscriber identityor a packet temporary mobile subscriber identity.
 19. The methodaccording to claim 14, wherein the controller (BSC2) of the accessnetwork (AN) is a base station controller or a radio network controller.20. The method according to claim 14, wherein the mobile communicationsystem is a global system for mobile communication or a universal mobiletelecommunication system.
 21. A mobile device (MS) suitable for sendinga message to a first network server (MSC1) in a server pool (CNSP) of amobile communication system, the mobile communication system having acontroller (BSC2) of an access network (AN) connectable to the firstnetwork server (MSC1) and at least one further network server (MSC2) inthe server pool (CNSP), wherein service points are defined and one ormore of the service points are allocated uniquely to each of the networkservers (MSC1, MSC2) in the server pool (CNSP), at least one of thenetwork servers (MSC1, MSC2) having allocated at least two of theservice points, the mobile device (MS) comprising: means to receive atemporary identity including a selected service point being selectedfrom the one or more service points allocated to the first networkserver (MSC1); and means to extract the selected service point from thetemporary identity, and to send the selected service point to thecontroller (BSC2) for applying a routing algorithm for routing themessage to the first network server (MSC1).
 22. An mobile communicationsystem having a network server (MSC1) in a server pool (CNSP), theserver pool having at least one further network server (MSC2), thenetwork server (MSC1) being connectable to a controller (BSC2) of anaccess network (AN), the network server (MSC1) having allocated at leasttwo service points that uniquely identify the network server (MSC1) inthe server pool (CNSP), the mobile communication system furthercomprising: means for receiving a request for an assignment of atemporary identity for a mobile device (MS); means for assigning thetemporary identity and including one selected service point beingselected from the two or more service points allocated to the networkserver (MSC1) into the temporary identity; and means for sending theassigned temporary identity to the mobile device (MS).
 23. The mobilecommunication system according to claim 22, further comprising means forre-allocating the service points to the network servers (MSC1, MSC2) inthe server pool (CNSP).
 24. The mobile communication system according toclaim 23, wherein the service points are allocated depending on a loadof at least one of the network servers (MSC1, MSC2) in the server pool(CNSP).
 25. The mobile communication system according to claim 23,wherein the service points are allocated depending on a load of a linkbetween the controller (BSC2) of the access network (AN) and one of thenetwork servers (MSC1, MSC2) in the server pool (CNSP).
 26. The mobilecommunication system according to claim 22, wherein the network server(MSC1) selects the selected service point.
 27. The mobile communicationsystem according to claim 22, wherein the temporary identity is assignedbased on location information of the mobile device (MS).
 28. The mobilecommunication system according to claim 22, wherein the controller(BSC2) of the access network (AN) is a base station controller or aradio network controller.
 29. The mobile communication system accordingto claim 22, wherein the mobile communication system is a global systemfor mobile communication or a universal mobile telecommunication system.